1. Field of the Invention
The present invention relates to a rectifier circuit which uses a diode and a power supply circuit which uses the rectifier circuit. More particularly, the present invention relates to a semiconductor device which uses the rectifier circuit or the power supply circuit and can perform wireless communication.
2. Description of the Related Art
Technology by which a signal is transmitted and received without contact between media (RF tags) each incorporating an integrated circuit and an antenna (RFID: Radio Frequency Identification) has been put to practical use in various fields and has been anticipated to further expand the market as a new mode of information communication. As the shape of an RF tag used for an RFID, a card shape or a chip shape which is smaller than such a card shape are employed in many cases; however, various shapes can be employed in accordance with an application.
As for RFID, communication between a reader, a reader/writer, or an interrogator and an RF tag can be performed with a radio wave. Specifically, a radio wave generated from an interrogator is converted into an electric signal by an antenna in an RF tag, and an integrated circuit in the RF tag is operated in accordance with the electric signal. Then, the radio wave modulated in accordance with an electric signal which is outputted from the integrated circuit is generated from the antenna; thus, a signal can be transmitted to the interrogator without contact. Here, the interrogator also has an antenna.
Note that RF tags can be broadly categorized into two types: active RF tags and passive RF tags. An active RF tag incorporates a primary battery and does not generate electric energy in the RF tag. On the other hand, a passive RF tag can generate electric energy in the RF tag with the use of a radio wave generated from an interrogator. Specifically, after a radio wave received from the interrogator is converted into an AC voltage by an antenna, the AC voltage is rectified by a rectifier circuit and then supplied to each circuit in the RF tag as a power supply voltage by using a smoothing capacitor or the like.
A structure of a rectifier circuit which uses one diode and a smoothing capacitor connected to an output side of the rectifier circuit is disclosed in Patent Document 1 (Japanese Patent No. 2909867 (p. 6, FIG. 1)). FIG. 18 illustrates the structure of the rectifier circuit and the smoothing capacitor which are disclosed in Patent Document 1. In the rectifier circuit illustrated in FIG. 18, a diode 800 is connected between an input terminal 801 and an output terminal 802. An anode and a cathode of the diode 800 are disposed on the input terminal 801 side and the output terminal 802 side, respectively. In addition, one of two electrodes of a capacitor 803 is connected to the output terminal 802, and the other is connected to a ground (GND).